This invention relates to a primer composition for priming the surface of a substrate to improve the adhesion of a sealant composition to such a surface. More particularly, this invention relates to a primer composition for priming the surface of a substrate which is non-porous, such as glass.
Urethane sealants and adhesives are known to provide high tensile strengths and tear strengths when used to bond materials. Such sealants and adhesives are especially suitable for use in automobile manufacture for the bonding of a windshield to an auto body, wherein the bonding imparts additional structural integrity to the automobile body. However, some urethane sealants do not bond glass to another substrate sufficiently without the use of a primer to prime the non-porous substrate. Primers for use in improving the bonding of glass to substrates are known and described, for example, in JP-57-3331A (1982), which discloses a primer composition for glass comprising a mixture or reaction product of an epoxy silane and a silane which has a functional group which is active with respect to epoxy groups, a reaction product of a polyisocyanate and at least one other silane compound, and a film-forming agent, plus carbon black or pigments, in the inorganic phase, as well as primer compositions comprising the reaction products of certain amino silanes and epoxy silanes, plus a silicone resin and carbon black. U.S. Pat. No. 4,963,614 discloses a primer composition for glass comprising a silane coupling agent, a reaction product of a polyisocyanate and a silane compound, a film-forming agent, and an acidic carbon black having a pH of from 2.5 to 4. U.S. Pat. No. 4,963,614 also teaches that suitable film-forming agents include polyester resins, chlorinated rubber, polyvinyl chloride resins, polyacrylate resins, epoxy resins, silicone resins, and ethylene bis-vinylacetate prepolymers. Finally, U.S. Pat. No. 4,981,987 discloses an adhesion improver comprising certain reaction products of amino compounds, carbonyl compounds, and epoxy compounds. However, the primer compositions referred to above are often cumbersome to prepare or have adhesion characteristics which are less than desirable. Therefore, glass primers with sufficient adhesion characteristics to non-porous substrates which are more easily prepared are desirable.